package com.bsh.utils;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
 
 
 
public class Base64 {
    private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
    /**
     * data[]进行编码
     * @param data
     * @return
     */
        public static String encode(byte[] data) {
            int start = 0;
            int len = data.length;
            StringBuffer buf = new StringBuffer(data.length * 3 / 2);
 
            int end = len - 3;
            int i = start;
            int n = 0;
 
            while (i <= end) {
                int d = (((data[i]) & 0x0ff) << 16)
                        | (((data[i + 1]) & 0x0ff) << 8)
                        | ((data[i + 2]) & 0x0ff);
 
                buf.append(legalChars[(d >> 18) & 63]);
                buf.append(legalChars[(d >> 12) & 63]);
                buf.append(legalChars[(d >> 6) & 63]);
                buf.append(legalChars[d & 63]);
 
                i += 3;
 
                if (n++ >= 14) {
                    n = 0;
                    buf.append(" ");
                }
            }
 
            if (i == start + len - 2) {
                int d = (((data[i]) & 0x0ff) << 16)
                        | (((data[i + 1]) & 255) << 8);
 
                buf.append(legalChars[(d >> 18) & 63]);
                buf.append(legalChars[(d >> 12) & 63]);
                buf.append(legalChars[(d >> 6) & 63]);
                buf.append("=");
            } else if (i == start + len - 1) {
                int d = ((data[i]) & 0x0ff) << 16;
 
                buf.append(legalChars[(d >> 18) & 63]);
                buf.append(legalChars[(d >> 12) & 63]);
                buf.append("==");
            }
 
            return buf.toString();
        }
 
        private static int decode(char c) {
            if (c >= 'A' && c <= 'Z')
                return (c) - 65;
            else if (c >= 'a' && c <= 'z')
                return (c) - 97 + 26;
            else if (c >= '0' && c <= '9')
                return (c) - 48 + 26 + 26;
            else
                switch (c) {
                case '+':
                    return 62;
                case '/':
                    return 63;
                case '=':
                    return 0;
                default:
                    throw new RuntimeException("unexpected code: " + c);
                }
        }
 
        /**
         * Decodes the given Base64 encoded String to a new byte array. The byte
         * array holding the decoded data is returned.
         */
 
        public static byte[] decode(String s) {
 
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            try {
                decode(s, bos);
            } catch (IOException e) {
                throw new RuntimeException();
            }
            byte[] decodedBytes = bos.toByteArray();
            try {
                bos.close();
                bos = null;
            } catch (IOException ex) {
                System.err.println("Error while decoding BASE64: " + ex.toString());
            }
            return decodedBytes;
        }
 
        private static void decode(String s, OutputStream os) throws IOException {
            int i = 0;
 
            int len = s.length();
 
            while (true) {
                while (i < len && s.charAt(i) <= ' ')
                    i++;
 
                if (i == len)
                    break;
 
                int tri = (decode(s.charAt(i)) << 18)
                        + (decode(s.charAt(i + 1)) << 12)
                        + (decode(s.charAt(i + 2)) << 6)
                        + (decode(s.charAt(i + 3)));
 
                os.write((tri >> 16) & 255);
                if (s.charAt(i + 2) == '=')
                    break;
                os.write((tri >> 8) & 255);
                if (s.charAt(i + 3) == '=')
                    break;
                os.write(tri & 255);
 
                i += 4;
            }
        }
         
}